All Years Seminars
[INMA] 2006-11-14 (14.00 pm) : "Control performance criteria in data-based control design"
At Euler building
Speaker :
Bazanella, Alexandre
Abstract :
Control performance criteria are a key element in control systems theory.
Not only they are fundamental from a conceptual point of view but this concept also
leads to a large variety of design methods, which are formulated as optimization problems.
For model-based design methods, the relevant properties of such criteria (convexity, uniqueness of minima, etc)
have been largely explored - although not always explicitly. On the other hand, it has been found that a limiting
factor in the application of data-based control design methods (such as IFT, but not restricted to it) is the convergence
to local minima of the criterion. Mainly - but not exclusively - motivated by that, we have been studying the "shape" of
different control performance criteria: model following, reference tracking, minimum variance, cheap control, etc, as
well as their combinations. We have determined conditions under which the criteria are "well-behaved". These conditions
involve mainly the data set, the initial condition for the optimization and the performance criterion itself. The results indicate
how to design the experiments and/or initialize the optimization so that it will succeed. They also suggest the use of cautious
control in the way to achieve the desired performance.
[INMA] 2006-11-07 (14.00 pm) : "FastICA, RQI and Its Generalisations: On the Interplay between Numerical Linear Algebra & Geometric Optimisation &ignal Processing."
At Euler building
Speaker :
Knut Hüper (National ICT Australia Ltd
Systems Engineering and Complex Systems Research Program
Canberra, Australia
and
Research School of Information Sciences
The Australian National University
Canberra, Australia/Cesame)
Abstract :
One of the state of the art algorithms for linear Independent
Component Analysis in Signal Processing is FastICA, developed by the
Finnish school. This very efficient algorithm enjoys nice
interpretations similar to the socalled Rayleigh-Quotient-Iteration
(RQI) well known to the Numerical Linear Algebra community. It can be
considered as an optimisation procedure on a manifold related to
intrinsic Newton-type iterations. We will discuss some of the known
facts of FastICA and then present more recent results towards
parallel implementations and better convergence properties.
This is joint work with Hao Shen.
[INMA] 2006-10-31 (14.00 pm) : "Using differential geometry for modelling dynamics of thermodynamical systems"
At Euler building
Speaker :
Audrey Favache (IMAP)
Abstract :
The state of thermodynamical systems can be described via some variables like energy, volume,
entropy, mass, temperature etc. But these quantities cannot vary independently. The laws of thermodynamics
impose the way they are linked together. Differential geometry provides tools to describe those relations. More
precisely contact structures allow to describe the thermodynamical model, whereas the contact Hamiltonian function
allows to describe the dynamics.
In this presentation, we will show how the physics of the system are related to the abstract concepts of differential geometry
and how it is possible to use the tools of differential geometry to analyze the system dynamics.
[INMA] 2006-10-27 (16.15 pm) : "P-multigrid et discrétisation discontinues"
At Salle séminaire TERM, Bâtiment Stevin
Speaker :
Koen Hillewaert
(cenaero)
Abstract :
[INMA] 2006-10-26 (16.30pm) : Colloquium CESAME/MAPA "Effaçabilité et rectifiabilité : le problème de Painlevé."
At Auditoire Ch.-J. de La Vallée Poussin (cycl 01)
Speaker :
Hervé Pajot (Université de Grenoble)
Abstract :
Un compact E du plan complexe est dit effaçable pour les fonctions holomorphes bornées si toute fonction
holomorphe bornée en dehors de E admet une extension holomorphe sur le plan complexe tout entier.
Un théorème de Riemann stipule que tout singleton est effaçable. Le problème de Painlevé consiste à caractériser
géométriquement les ensembles effaçables. Ce problème d'analyse complexe est devenu un problème d'analye harmonique
(continuité d'intégrales singulières) et de théorie de la mesure géométrique (rectifiabilité). Le but de l'exposé sera d'évoquer l'historique de ce problème,
de la thèse de Painlevé à la solution de Tolsa en 2003. Les nombreux problèmes ouverts à la suite du résultat de Tolsa seront aussi discutés.
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